1. Field of the Invention
This invention relates to fire-retardant compositions. In one aspect, the invention relates to novel compositions containing certain surface-active agents useful in increasing the rate and extent of penetration of the composition into wood and wood products. In another aspect, the invention relates to the use of these novel compositions.
2. Description of the Prior Art:
Most fire-retardant compositions must be applied to wood by a pressure treatment to achieve sufficient modification of the wood to reduce the flame-spread rating, one measure of fire-retardancy. However, inorganic, fire-retardant phosphate salts, such as mono and diammonium phosphate, polyphosphate, etc., make high solid solutions that can be applied by surface penetrating techiques, such as spray or roller coating, that results in an effective flame-spread control but upon exposure to various humidity conditions, these salts migrate to the surface. This migration not only depletes the salt content of the substrate, rendering it less fire-retardant, but can also severely disfigure the surface. Compositions containing these fire-retardant phosphate salts in combination with a partially hydrolyzed poly-2-oxazoline demonstrate substantially inhibited migratory properties but do not penetrate wood with sufficient speed and in sufficient quantity to permit their use on a production line operation employing surface penetrating techniques.
While surfactants are considered useful in surface applications generally, certain articles, such as "Treatment of Wood with Aqueous Solutions: Effect of Wetting Agents", Indus. Engin. Chem., 32, 809 (1940) by the Forest Products Laboratory at Madison, Wisconsin, Forest Service U.S. Dept. of Agriculture, have been published which teach that surfactants do not increase the rate or extent of penetration of water or solutions into the surface pores of wood. Most anionic types, such as Aerosol.RTM. OT and Dowfax.RTM. 2A1 and 3B2, are generally not compatible with concentrated fire-retardant salt solutions and eventually precipitate. Many nonionic surfactants are compatible with concentrated fire-retardant salt solutions but demonstrate no effect on the rate and extent of penetration of the salt into the wood.